The diversity, distribution pattern, and conservation status of endemic species were obtained by analysis of catalogued specimens collected by fieldwork carried out by the authors at various times in different regions in Iran since 2002. The Iranian endemic ichthyofauna includes 51 species and forms a significant part of the total species known from this country, so that new endemic species are being described almost every year. The highest endemicity is found in the Tigris-Karoun basin in the west, followed by the Kor River and the Persian Gulf basins in the south. Creation of the landlocked basins played an important role in speciation and diversification of Iranian endemic fishes. In addition, the biogeographic situation and geological history of the Iranian plateau, as well as the various climate conditions and consequent different habitat types, may have contributed to this high diversity. Numerous threats are known to seriously affect this diversity; some of the endemic species are going to be extinct in the near future. Human-induced disturbances (i.e. Fish introductions, pollution, and, in particular, habitat destruction and unusual methods of fishing) and natural disturbances (particularly drought during the past 10 years) have drastically affected endemic ichthyodiversity in Iran.